1. FIELD OF THE INVENTION
This invention relates to an improvement in a stopper plug to be inserted in a tap hole of a converter, especially an LD converter, and more specifically, to a stopper plug which comprises a molding of a refractory material, a fibrous substance and a binder.
2. DESCRIPTION OF THE PRIOR ART
When a slag in a steel-making furnace flows out into a ladle together with the molten steel during tapping, a part of the slag is suspended in the molten steel without surfacing on the molten steel, and also the sulfur and phosphorus in the slag revert into the molten steel. Accordingly, the present practice is to perform tapping in such a manner that the slag in the furnace does not flow out together with the molten steel.
The tapping from a converter, especially an LD converter, is carried out by gradually tilting the converter in order to release the molten steel from a tap hole located at the upper part of the wall, with the tap hole being plugged previously with a wooden stopper plug. The plug is forced out of the hole as a result of the pressure of the molten steel which increases as the converter is tilted. As for the opening of the tap hole, it is important that the tap hole is opened by the pressure of the molten steel which increases as the tilting of the converter proceeds, and is not opened by the low pressure of the molten steel in an early stage when the molten steel begins to cover the plug. This prevents the slag floating on the molten steel from flowing out of the tap hole together with the molten steel. The tilting is stopped after almost all of the molten steel has flowed out and before the slag begins to flow out.
The stopper plug for the tap hole is made by shaping a piece of wood so that the shape of the plug conforms to that of the tap hole. However, it is very difficult to shape a piece of wood into a shape exactly corresponding to the tap hole.
When the converter has been used many times, the brick at the tap hole is corroded by the molten steel and the hole is deformed. Furthermore, the stopper plug does not have a shape corresponding exactly to the tap hole. The mere insertion of the stopper plug in the tap hole does not ensure complete plugging of the tap hole. Accordingly, the tap hole must be plugged by filling a sealing material such as mortar around the stopper plug.
As described above, the stopping of the tap hole is very complicated. Also, since the stopper plug is firmly fixed by the mortar, frequently the plug is not forced out by the pressure of the molten steel caused by the tilting of the converter.